This invention relates generally to vehicles and specifically to a low speed traction steered powered tricycle that is very stable, lightweight and highly maneuverable.
The term powered as used herein is intended to apply to both battery powered and gasoline engine powered vehicles. Both indoor and outdoor operation of the powered vehicle of the invention is contemplated. It should be noted that the present invention is represented herein as a powered chair (FIG. 1), but it could benefit other low speed vehicles such as, without imitation, a riding lawn mower, (FIG. 2) or a golf cart (FIG. 3).
Contemporary powered chairs may be divided into two categories: those that steer by selectively operated traction wheels and those that steer by turning the front wheel or wheels.
The traction-steered vehicles are commonly referred to as powered wheelchairs. They are operated by a single joystick that interacts with a very complicated electronic control system for switching and modulating the requisite high current, low voltage, battery power. The electronic control systems are expensive, subject to radio wave interference and prone to service problems. Some electronic controls have been reported to spontaneously energize their vehicle motors when exposed to radio frequency interference, such as that from a cellular telephone. The potential danger is such that warning labels are now required in those vehicles and, in some instances, product recalls are under consideration.
Powered wheelchairs are generally not intended for use outdoors on unpaved surfaces, such as grass, dirt and bumpy trails. The chairs employ two gear motors to independently and directly drive the left and right wheels. Most powered wheelchairs have two rear-mounted drive wheels and two front caster wheels, all supported on a rigid frame structure. Over uneven or mildly bumpy terrain, the wheelchairs deliver a harsh ride as weight is shifted randomly between diagonal pairs of wheels. With this type of configuration steering is also uncontrollable since loss of traction of one drive wheel results in the opposite drive wheel thrusting the vehicle into a turn until traction is regained. This causes the vehicle to randomly dart to the left and to the right. The tendency could be overcome with a four-wheel suspension system but such a complicated solution is neither suitable nor practical for a powered wheelchair.
It should also be noted that, due to the requisite high ratio gearing of the vehicle, it is practically impossible to over drive the motors (to allow the vehicle to coast) when traveling downhill This inability to coast greatly reduces its range of travel, particularly in graded or hilly areas.
Powered chairs that directly steer a wheel (or a pair of wheels) are commonly referred to as scooters. Most scooters employ a tricycle configuration, with steering of the front wheel being accomplished by means of a handlebar. A three wheeled vehicle or tricycle has the advantage of maintaining a consistent load on each wheel and, in comparison with the powered wheelchair described above, provides a relatively smooth ride over bumpy surfaces. On the other hand, scooters have a relatively large turning radius and are not well suited for indoor use.
Scooters employ a single gear motor that drives the rear wheels through a differential While the tricycle configuration maintains substantially equal loading of the drive wheels under all normal surface conditions, the differential is subject to traction loss due to split coefficient. This may occur for example, when either drive wheel loses traction on a wet or slippery surface resulting in neither drive wheel being able to provide a driving force. The result is that the vehicle user, who is often incapable of walking or significant unassisted movement, is literally stranded. The costs and weight of a differential are about the same as an extra motor and gear reduction mechanism, but the controls on the scooter are less complicated and more reliable than the joystick systems used on the powered wheelchairs discussed above.
Because of their front wheel steering and tricycle configuration, scooters are highly unstable at practically all speeds. A sudden turn of the handlebar will invariably cause the tricycle to tip. The centrifugal force acting on such a high center of gravity vehicle tends to throw the vehicle (and occupant) up onto the front wheel and the outside drive wheel (the wheel at the outside of the turning radius). Simultaneously, the wheel at the inside of the turning radius is lifted off the ground. If the occupant does not immediately steer out of the turn (which is sometimes impossible) a roll over will occur. Often at the onset of tipping, the occupant reflexively applies the brakes in an attempt to regain control This exacerbates the predicament, since braking increases the centrifugal force, and usually results in an instant rollover. Tipping is a classic problem with tricycle type vehicles and a unique means for overcoming the tipsy-tricycle syndrome is a primary feature of the present invention.
Powered wheelchairs and scooters are also bulky and heavy (generally weighing in the range of 150 to 250 pounds) and require special equipment to transport them. They are also very expensive items, and if the added cost of a specially equipped van with a power lift is considered, are prohibitive for most people. It is these major drawbacks that have prevented their widespread acceptance. The various shortcomings of the prior art powered wheelchairs and scooters, as well as hand-propelled wheelchairs are the subject of the copending parent application identified above.
The present invention provides a powered vehicle that is compact, inexpensive and maneuverable and will find ready application in its various forms as a safe and stable vehicle for all uses and by persons of all ages, provided that they have the use of both their arms. The present invention in its preferred embodiment as depicted in FIG. 1, offers numerous advantages over the prior art. It can be used on trails and various unpaved surfaces while maintaining control and traction and providing a smooth ride. The vehicle is highly maneuverable, which makes it ideal for negotiating tight spaces, such as those encountered indoors. Its freewheeling design permits coasting, which increases its range while mining battery weight. Its light weight and small size enables it to be transported by a conventional automobile (without special equipment) and its simplicity of design makes it inexpensive to own and operate, and reliable to use. A major advantage is that the powered vehicle of the invention remains safe and stable under all normally encountered road and operating conditions, and with all types of users.
Propulsion, steering, and braking of the inventive powered vehicle is provided by selectively engaging the periphery of the rear drive or traction wheels with corresponding motor-driven friction rollers or friction brake surfaces. The engagement between the friction rollers or brake surfaces and the traction wheels is controlled by a pair of manual control arms that the user simply moves down for propulsion and up for braking. Normal tuning is accomplished by engaging one friction roller with its corresponding traction wheel Very tight turns may be made by simultaneously engaging one friction roller with its associated traction wheel and engaging the opposite brake surface with its associated traction wheel. This configuration allows for the tight maneuvering necessary for indoor operation.
The inventive vehicle is also well suited for use on uneven or hilly surfaces. Its tricycle configuration keeps both driving wheels evenly loaded at all times, resulting in a smooth ride and predictable control. When both control arms are held down, both friction rollers are engaged with their corresponding traction wheels. This acts like a solid axle delivering torque to each traction wheel directly regardless of the coefficient of friction, unlike the operation that occurs with a differential.
The control arms are sprung-to-center so that the traction wheels are normally in a free wheeling state. The ability to coast greatly enhances the vehicle""s speed and range, particularly in hilly areas. The caster wheel is located in front rather than the rear to provide a self-steering effect when coasting. This allows the vehicle to coast straight with little or no steering input from the occupant.
The vehicle of the present invention is highly stable due to its tricycle configuration and traction steering. During a hard turn, with one traction wheel being driven and the other traction wheel being braked, any tendency to go into an unstable (tipping) condition is obviated due to the effects of centrifugal force, which automatically lifts the braking traction wheel on the inside of the turning circle.
The preferred embodiment incorporates a simple, inexpensive and highly reliable control system that uses electrical switches to energize the motor when either control arm is actuated. Two 12-volt batteries may be operated in series or in parallel to provide two basic travel speeds. The user may, however, operate the vehicle at desired lower speeds by xe2x80x9cjoggingxe2x80x9d the control arms to intersperse bursts of driving force with periods of coasting. Unlike the electronic control system described above, the simple electrical controls of the preferred embodiment are not affected by radio frequency signals or other airborne electrical interference.
While the preferred embodiment incorporates a DC permanent magnet motor, it should be understood that the invention is not to be so limited. A lightweight gasoline engine may offer advantages for outdoor use. A lightweight frame and transmission system minimizes weight, which permits a single motor to provide sufficient power for the vehicle. Whereas most battery powered vehicles weigh from 150 to 250 pounds, the powered vehicle of the invention weighs about 50 pounds. To further ease the effort of lifting the vehicle, the battery may be easily removed from the frame to reduce the vehicle weight by half As will be seen, the inventive powered chair also includes a comfortable, padded rigid seat, which is also easily removed to enable the powered vehicle to be transported in the trunk of a compact automobile.
A principal object of the invention is to provide a novel powered tricycle, with steady control and smooth ride characteristics on uneven surfaces, without a suspension.
Another object of the invention is to provide a powered tricycle that is stable and safe under all normally encountered operating conditions and terrain.
A further object of the invention is to provide a novel powered tricycle with improved traction on surfaces having a split coefficient of friction.
Still another object of the invention is to provide a novel powered tricycle with tight turning capability.
Yet another object of the invention is to provide a novel powered tricycle that can coast.
A still further object of the invention is to provide a novel powered tricycle that is small and lightweight enough for easy transportability.
Another object of the invention is to provide a novel powered tricycle that is highly reliable and inexpensive.